1. Field of the Invention
The present invention broadly relates to solar cell testing and, more particularly, is concerned with a method and apparatus for nondestructive extraction of glued coverslides from solar cell to facilitate testing and evaluation of the solar cells.
2. Description of the Prior Art
Solar cells are typically packaged with a transparent coverslide adhered thereto. The coverslide may be used to serve a variety of purposes: (1) to increase the emissivity of the solar cell and thereby provide a lower operating temperature which raises the electric power output of the cell; (2) to protect the solar cell from radiation damage; and (3) to serve as a substrate for UV or IR reflection filters to decrease operating temperatures and ensure higher cell efficiency.
However, oftentimes in the course of photovoltaic research and development, conditions may necessitate the extraction of the coverslide. For example, requirements for testing solar cells for electrical evaluation, radiation exposure, or thermal shock call for testing groups of uncovered solar cells. At other times, test requirements can call for a specific type of coverslide to be installed on a solar cell previously covered with an inappropriate cover, such as one which varies in optical and physical properties from those that are desired. Also, a fracture may occur in the coverslide of a solar cell prior to or during testing. Due to the large expense of individual cells, it is desirable to be able to remove the damaged coverslide and replace it with a new one.
Heretofore, the technique for coverslide extraction has been rather crude. In this technique, the solar cell with the coverslide adhered thereto are placed in a bottle partially filled with solvent. Then, the jar is gently shaked causing the solvent therein to agitate about the solar cell and initiated loosening of the glue around the edge of the coverslide. Some areas of the coverslide separate quickly from the solar cell while other areas separate more slowly. This uneven separation of the coverslide often rsults in the propagation of stess cracks in the solar cell due to curling thereof which effectively destroys the cell. In other instances, the coverslide cracks and breaks into several parts, one separated from the solar cell and the other still attached thereto. With use of this technique, about 75 percent of the time attempts to extract the coverslide have resulted in cracked coverslides and/or fractured solar cells. In view of the high cost of individual solar cells and the inadequate extraction techniques being used, coverslide extraction has been a bottleneck in certain areas of photovoltaic research and development.
Consequently, a need exists for a reliable coverslide extraction technique which will consistently result in separation of glued coverslides from solar cells without irreversible damage being done to the solar cells.